Experts say particulate matter found in the clouds may also be cause for health concerns, and are calling for more study to understand their potential impact.
"It is a matter of great magnitude, interest and importance for health," said Braulio Jimenez-Velez, a specialist in molecular and environmental toxicology at the University of Puerto Rico at Mayaguez, who is researching the issue.
African dust has prompted two health alerts this year in Puerto Rico for asthma sufferers and people with allergies, and the Dominican Republic also issued a lower-level warning.
Airborne particulate matter is connected to respiratory disease worldwide, usually among people with existing problems such as asthma. Parts of the Caribbean, such as Puerto Rico, have high asthma rates. However, no direct link between African dust and higher rates of asthma or lung cancer has been established.